1. Field of the Invention
The present invention relates to a method for forming a pattern which is suitable for use in formation of a fine pattern in, for instance, the manufacturing of semiconductor devices.
2. Description of the Prior Art
Hitherto, as techniques to form a resist pattern, photolithography using light, and electron beam lithography using electron beams, are used. In the photolithography and electron beam lithography, five steps of coating a resist, baking, exposing, developing, and post baking are necessary; and the wet process is used.
In the conventional photolithography as described above, since the a resolution of which is not longer than the wavelength of the light which is used for exposure cannot be obtained, the minimum pattern width which can be formed is limited to about 0.25 .mu.m. On the other hand, the use of X-ray lithography using X-rays whose wavelength is short and is about a few .ANG. in place of light has also been known. However, in this case, a large scale apparatus such as a synchrotron orbital radiation (SOR) apparatus is necessary as a light source. In addition, there is a problem that the construction of the optical system such as lens, mask, and the like is generally difficult.
In the conventional electron beam lithography as described above, when an electron beam is irradiated onto an electron beam resist, the trace of the electrons is made random by multiple scattering in the electron beam resist, so that the inherent resolution of the electron beam is lost. Therefore, the width of the pattern which can be formed by the conventional electron beam lithography is at most about 1000 .ANG.. It is extremely difficult to form a pattern of an ultrafine width of about 100 .ANG..
On the other hand, according to a method for forming a resist by an electron beam which has already been proposed by the same inventors as the present invention, although it is not publicly known (hereinafter, the resist formed by this method is referred to as an EBIR (Electron Beam Induced Resist)), by irradiating an electron beam whose beam diameter was finely converged onto the substrate in the atmosphere containing a raw material gas such as alkylnaphthalene, a resist pattern of an ultrafine width comprising amorphous hydrocarbon can be formed by the dry process. However, it is difficult to remove such a resist pattern comprising amorphous hydrocarbon unless the dry etching such as a reactive ion etching (RIE) is used. However, since there is a fear of occurrence of damages on the substrate and the like upon such a dry etching, a method for forming the resist pattern which can be removed by the wet process is desired.
As methods for forming a pattern, there has been known a method whereby by irradiating an electron beam onto a film to be etched in a carbonaceneous gas atmosphere, a carbonaceneous mask coating film is formed on the film to be etched (Japanese Patent Laid Open Publication No. Sho 61-0241). Also known is a method whereby a gas containing a deposition material as a component element is supplied onto a substrate which is cooled to 10.degree. C. or less, an electron beam is irradiated to a desired portion of the surface of the substrate, and the material is deposited onto the substrate (Japanese Patent Laid Open Publication No. Sho 62-42417). However, in these literatures publications there is no disclosure concerning the optimum conditions for forming a resist pattern of an ultrafine width.